The difference between a bad programmer and a good programmer is understanding. That is, bad programmers don't understand what they are doing, and good programmers do. Believe it or not, it really is that simple.
短短一段话，蕴含了很多内容：bad programmer, good programmer, understanding, and the most important, simple. simple 这个字，在这里用得非常到位，一语双关，既说明了道理就这么简单，又暗指书名中的 simplicity。
全书都是围绕 simple 和 simplicity 来展开论述的。为什么要强调 simple (simplicity)？是因为复杂的系统容易出错！使系统更为 robust 的方法就是降低系统的复杂度，使系统简化，代码简单。道理就这么简单（it really is that simple）。
There are somple examples of consistency in the real world. In much of Asia, people use chopsticks to eat. In the Americas and Europe, peoiple use forks. Okay, that's two different methods of eating, but overall it's pretty consistent, in any given area. Now imagine if every time you went to somebody's house, you had to learn some whole new way of eating. Maybe at Bob's house they eat with scissors, and at Mary's house they eat with flat pieces of cardboard. Eating would get pretty complex, wouldn't it?
it's the same in programming -- without consistency, things get very complex.